1. Field of the Invention
The present invention relates to a flow channel for a heat exchanger for heat transfer between a first fluid and a second fluid, comprising: a channel casing having an interior space surrounded by a channel casing inner surface; a number of partitions, which are arranged in the interior space of a channel casing inner surface, the flow channel which has a flow-through cross section, transverse to a flow channel axis, for guiding the first fluid in the interior space. The invention relates further to a heat exchanger for heat transfer between a first fluid and a second fluid, comprising: a block for the separate and heat-exchanging guiding of the first and second fluid, and a fluid connection for the first fluid; said block which has a housing with a chamber through which the second fluid can flow, and a block closure element for separating the chamber and the fluid connection. The invention relates further to an exhaust gas recirculation system, a charge air supply system, and a use of the heat exchanger.
2. Description of the Background Art
A flow channel for use in a heat exchanger is known German Patent Application No. DE 37 316 69 A1 of the applicant, and which is herein incorporated by reference.
Heat exchangers have the task of cooling a hot first fluid with the aid of a colder second fluid, so that the first fluid, particularly an exhaust gas or exhaust gas/air mixture or charge air, can be mixed into the intake air for an internal combustion machine, for example, an engine. The second fluid can be formed as a coolant, for example, a liquid or gaseous or mixed liquid-gas coolant, which at any rate in the case of a liquid coolant can be removed from the cooling circuit of the internal combustion engine. Basically, to increase the thermodynamic efficiency, the aim is cooling to as low a temperature level as possible. It is known that the concept of a cooled exhaust gas recirculation system or cooled charge air can be used to reduce pollutants, particularly nitrous oxides, in the exhaust gas.
Specifically in regard to the requirements of contemporary engines, it is possible with exhaust gas recirculating coolers to meet the continuously increasing requirements for exhaust gas pollution control. By cooling the exhaust gas and resupplying the cooled exhaust gas, the combustion temperature in the engine is reduced and leads to reduced NOx emissions. Increasing requirements for pollutant reduction have resulted in the further development of known cooler concepts and the proposal of new cooler concepts.
A flow channel in a prior-art heat exchanger can be made from a steel or stainless steel material. Here, in particular, the corrosion resistance of steel and stainless steel materials have proven valuable.
It also turned out that flow channels made from aluminum or based on an aluminum material can be made at a considerably lower cost.
To improve heat transfer in a flow channel sufficiently, a flow channel, as explained heretofore, can be typically fitted with a number of partitions arranged in an interior space on a channel casing inner surface. Basically, the number of partitions can contribute to increasing the heat transfer. With an excessive number of partitions, however, the risk rises considerably of a blockage by soot particles, which are present, for example, in the exhaust gas. It turned out that in too narrow through-passage regions in the flow channel, which are defined substantially by the flow-through cross section, a flow channel is fouled relatively rapidly and in the worst case can become partially clogged. This process as well as other measures for increasing heat transfer also increase in a contrary manner the pressure loss present in a flow channel, which is not desirable within the scope of modern heat exchanger concepts.
In addition to the design of a flow channel with an extruded channel casing as disclosed in DE 37 316 69 A1, there are other types of designs as are known, for example, from German Pat. No. DE 10 225 812 C1, German Pat. Appl. No. G 94 065 59.4, Unexamined German Pat. Appl. No. DE 36 153 00 C2, and German Utility Pat. No. DE 202 05 200 U1. However, the flow channels specified therein are intended and designed specifically for a particular application. Thus, for example, U.S. Pat. No. 5,184,672 discloses a flow channel for a heat exchanger in the form of a condenser which is fitted with flat tubes through which a liquid coolant flows. U.S. Pat. No. 3,486,489 discloses an oil cooler which is fitted with flat tubes through which oil to be cooled flows. U.S. Pat. Appl. No. 2005/0061488A1 discloses a heat exchanger which is designed for cooling oil and whose flow channels are designed for conducting the oil to be cooled. The flow-through cross section of the flow channels described therein is designed specifically for the flowing through of oil. In U.S. Pat. Appl. No. 2005/0061488A1, the flow-through cross section is characterized by a power ratio between 3.9 and 8.5, which is defined as a ratio of a wettable periphery in millimeters to a flow-through cross-sectional area of the metal tube in mm2.
Such flow channels designed for guiding liquid fluids are not suitable for use in a heat exchanger of the type specified heretofore. The heat exchanger of the aforementioned type is designed in particular as an exhaust gas heat exchanger and/or charge air heat exchanger. In this case, the first fluid is gaseous or a vapor, thus, for example, an exhaust gas or an exhaust gas/air mixture or charge air. In this case, the second fluid is a coolant, in particular a liquid or gaseous or mixed liquid-gas coolant. With regard to the above-explained problems, it is desirable to realize an improved design concept for a flow channel.